Structural and magnetic studies on vanadium spinel MgV2O4

Mamiya, Hiroaki; Onoda, Mitsuko; Furubayashi, T.; Tang, Jingling; Nakatani, I.

doi:10.1063/1.364518

Cited by 95 publications

(101 citation statements)

References 5 publications

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“…In one family of cases the spin-Peierls transition can be first order, as indeed observed in many pyrochlore antiferromagnets [7][8][9][10][11][12].…”

Section: Fig 1 the Pyrochlore Latticementioning

confidence: 99%

“…A resonance highly reminiscent of such modes has been observed by S.-H. Lee et al [12] in ZnCr 2 O 4 . The strings should also be observable in ZnV 2 O 4 where a structural distortion and a collinear Néel order at low temperatures have been firmly established [8,10]. A weaker feature might exist in the itinerant magnet YMn 2 .…”

Section: Fig 1 the Pyrochlore Latticementioning

confidence: 99%

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Order by Distortion and String Modes in Pyrochlore Antiferromagnets

2002

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We study the effects of magnetoelastic couplings on pyrochlore antiferromagnets. We employ Landau theory, extending an investigation begun by Yamashita and Ueda for the case of S = 1, and semiclassical analyses to argue that such couplings generate bond order via a spin-Peierls transition. This is followed by, or concurrent with, a transition into one of several possible low-temperature Néel phases, with most simply collinear, but also coplanar or mixed spin patterns. In a collinear Néel phase, a dispersionless string-like magnon mode dominates the resulting excitation spectrum, providing a distinctive signature of the parent geometrically frustrated state. We comment on the experimental situation.Geometrically frustrated magnets [1][2][3] are examples of strongly interacting systems: the vast degeneracy of their classical ground states makes them highly susceptible even to small perturbations. By analogy with quantum Hall systems, where the Landau levels are also macroscopically degenerate, one expects a variety of phases in perturbed frustrated magnets, from Néel states to spin glasses or liquids, with valence-bond solids along the way.Probably the world's most frustrated spin system is the classical Heisenberg antiferromagnet on the pyrochlore lattice ( Fig. 1) where spins reside at vertices of tetrahedra. The number of its classical ground states, which are attained when total spin on each tetrahedron S tot = 4 i=1 S i = 0, is so large that, exceptionally, it does not order at any finite temperature [4]. In real compounds, deviations from the classical Heisenberg model (e. g. dipolar interactions, single-ion anisotropy or quantum fluctuations) determine which ground state is selected at the lowest temperatures. FIG. 1. The pyrochlore latticeIn this note, we discuss an elegant mechanism for lifting the frustration through a coupling between spin and lattice degrees of freedom. The high symmetry of the pyrochlore lattice and the spin degeneracy drive a distortion of tetrahedra via a magnetic Jahn-Teller ("spinTeller") effect. The resulting state exhibits a reduction from cubic to tetragonal symmetry and the development of bond order in the spin system with unequal spin correlations S i · S j on different bonds of a tetrahedron. In the ordered phase, there are 4 strong and 2 weak bonds per tetrahedron-or vice versa. This phenomenon was uncovered by Yamashita and Ueda [5] for pyrochlore antiferromagnets with spins S = 1, for which they described an AKLT-style wavefunction [6] with the requisite bond order. In the following we study this phenomenon in the semiclassical limit with added insight from Landau theory, and discuss its consequences for the excitation spectrum. As many of the candidate systems have moderately large spins and order at finite temperatures, our methods should work well-in particular, they allow us to treat the Néel order that can (and experimentally does) appear in addition to the bond order.We begin by identifying a two-component bond order parameter at the level of a single tetrahedron an...

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“…In one family of cases the spin-Peierls transition can be first order, as indeed observed in many pyrochlore antiferromagnets [7][8][9][10][11][12].…”

Section: Fig 1 the Pyrochlore Latticementioning

confidence: 99%

Section: Fig 1 the Pyrochlore Latticementioning

confidence: 99%

Order by Distortion and String Modes in Pyrochlore Antiferromagnets

2002

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“…Furthermore, the AV 2 O 4 normal spinels can be divided into two groups based on the A ions. One group includes AV 2 O 4 (A = Cd [2][3][4], Mg [5][6][7][8][9], Zn [10,11]) with non-magnetic A ions. In these three materials, the orbital ordering (OO) transition drives a cubic to tetragonal structural phase transition at low temperatures which relieves the geometrical frustration of the Vpyrochlore sublattice and leads to an antiferromagnetic transition of the V 3+ ions.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Sinclair

Cao

et al. 2015

Phys. Rev. B

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The magnetic and structural properties of single crystal Fe1−xCoxV2O4 samples have been investigated by performing specific heat, susceptibility, neutron diffraction, and X-ray diffraction measurements. As the orbital-active Fe 2+ ions with larger ionic size are gradually substituted by the orbital-inactive Co 2+ ions with smaller ionic size, the system approaches the itinerant electron limit with decreasing V-V distance. Then, various factors such as the Jahn-Teller distortion and the spin-orbital coupling of the Fe 2+ ions on the A sites and the orbital ordering and electronic itinerancy of the V 3+ ions on the B sites compete with each other to produce a complex magnetic and structural phase diagram. This phase diagram is compared to those of Fe1−xMnxV2O4 and Mn1−xCoxV2O4 to emphasize several distinct features.

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“…In a strict sense, we cannot be certain that g B (Zn) = 0 even in the bulk specimens synthesized by a solid-state reaction at 1523 K. In our analysis, the magnitude of δb indicates that Zn 2+ in the B site is less than 10 % even in the extreme case of g B (Mn) = 0. At present, we must recall that even small amounts of nonmagnetic substitution in the B-sublattice seriously affect the magnetic properties when homogeneous antiferromagnetic couplings predominate magnetic interactions between the topologically frustrated spins in the B-sublattice [15,17]. Such mechanism, however, cannot be directly applied to this system because the effectively ferromagnetic B-A-B couplings are much larger than J BB .…”

Section: Ionmentioning

confidence: 98%

Structural and Magnetic Properties of Dilute Spinel Ferrites: Neutron Diffractometry and Magnetometry Investigations

Mamiya¹,

Terada²,

Kitazawa³

et al. 2011

Journal of Magnetics

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Magnetic properties of highly zinc-substituted manganese ferrites are discussed on the basis of cation distribution. High throughput neutron powder diffractometry indicates that the prepared samples possess a nearly normal spinel structure, where the substitution of nonmagnetic zinc ions mainly causes the dilution of magnetic ions in the A-sublattice and consequently affects bond-randomness in the B-sublattice. On the other hand, the estimated occupancy of manganese ions in the B site indicates that random anisotropy effects due to local Jahn-Teller distortions gradually weaken with the substitution. Bulk magnetometry indicates that the substitution smears the transition from a paramagnetic phase to a soft-magnetic phase. Furthermore, at lower temperatures, such a soft-magnetic phase is destabilized and a magnetic glassy state appears. These features of the magnetic properties of dilute spinel ferrites are discussed from the viewpoint of the above-mentioned various types of disorders.

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Structural and magnetic studies on vanadium spinel MgV2O4

Cited by 95 publications

References 5 publications

Order by Distortion and String Modes in Pyrochlore Antiferromagnets

Order by Distortion and String Modes in Pyrochlore Antiferromagnets

Evolution of the magnetic and structural properties ofFe1−xCoxV2O4

Structural and Magnetic Properties of Dilute Spinel Ferrites: Neutron Diffractometry and Magnetometry Investigations

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